Fermentation processes generally produce end products that need to be separated and/or recovered for further use. In many fermentation processes in which organic acids are produced, for example, a base is added to maintain the desired pH as the organic acids are produced. The addition of the base converts the acid to its salt form. Stronger acids such as mineral acids are added to convert the salt form of the organic acid back to its acid form and to facilitate the separation and recovery of the organic acid product. This series of treatments can produce a variety of salt by-products, at least some of which may have to be discarded as undesirable waste.
U.S. Patent Publication 2007/0015264 discloses the production of ammonium salts of organic acids. The ammonium salt composition is produced by fermenting a carbohydrate in the presence of a magnesium compound to produce a magnesium salt of an organic acid. The magnesium salt composition that is produced is treated with an ammonium base to produce the ammonium salt of the organic acid and a magnesium base, which can be used in subsequent fermentations, but leaves the organic acid in the ammonium salt form.
U.S. Pat. No. 5,598,744 discloses a process for producing succinic acid from a succinate salt. The method involves the formation of diammonium succinate, either by using an ammonium ion based material to maintain neutral pH in the fermentor or by substituting the ammonium cation for the cation of the succinate salt created in the fermentor. The diammonium succinate is reacted with a sulfate ion, such as by combining the diammonium succinate with ammonium bisulfate and/or sulfuric acid at sufficiently low pH to yield succinic acid and ammonium sulfate. The ammonium sulfate is advantageously cracked thermally into ammonia and ammonium bisulfate. The succinic acid can be purified with a methanol dissolution step. Various filtration, reflux and reutilization steps can also be employed.
It would be desirable to find alternative or additional processes of producing organic acids such that co-production of salt compounds are reduced or that co-produced salt compounds are in a form that reduces undesirable waste. It would be further desirable to produce organic acids using a process in which the organic acid is relatively easy to separate and recover. It would also be desirable to enhance the quantity of acid produced relative to any salt co-product that may also be produced.